Cannibalistic fish?

[Egotistical Moose]

Hi, this is my first thread here, and I have a few questions about fishkeeping. Before I say anything, I'd like to get on my knees and BEG for forgiveness for not being active -- before I set up my tanks, it was painful enough to think about fish while my beautiful new 75-gallon aquarium sat in the corner, gathering dust!

Well, I'm pleased to say that I have a small hospital tank (though it's pretty much simply a small tank, now that I've decided on getting larger fish than I expected!) that is up and running and has been cycled. It's twelve gallons, but does not have a particularly powerful filter. That's okay, since I have some very hardy fish in there at the moment, three (now two) blue damsels and a Percula Clownfish named the Clownfish Formerly Known as Billie Jean. They're my pride and joy, since they have gained a spectacular amount of color since I bought them. I thought that they looked great at the fish store, but now they look simply marvelous, and are at the peak of good health.
Well, the other day, I noticed that the smallest damsel (Thriller) was looking a bit frayed. Its fins were slightly damaged and worn away, and it was hiding behind a small piece of live rock until I came up to feed it. Thoughts of quarantining the tank and fish again raced through my mind, and I searched through all my fish books for diseases that my poor little damsel may have caught. It didn't seem to have many symptoms, and the other fish were looking fine, so I pushed it out of my mind.
Yet today, I noticed that the poor little fish was floating upside down! It was breathing steadily, yet its beautiful fins were nearly no more. I stared at it for a while, hope for Thriller draining, when my biggest damsel (Annie) came up -- and stripped a bit of Thriller's flesh away before devouring it!
I couldn't believe it -- my peaceful little damsels were eating each other. All my fish were fed very well, and receive one serving of pellets, one serving of zooplankton a day. I understand that some damsels are very territorial fish, and were likely to n** at each other, but I have never heard of peaceful, hardy little damsels eating one another!
There's been no sign of aggression from my clown or medium-sized blue damsel, yet now I fear for both of them. It's a small tank, one that we did not intend to keep them in forever, so perhaps should I return my two healthy damsels to the fish store? Should I separate the big damsel from the clown and remaining damsel?
P.S. I have no tank dividers, so I took a chance and put the unhealthy damsel in my larger, cycling tank. Sure that the other fish weren't letting it feed, I got my zooplankton out and placed individual small lumps into its mouth. This took about thirty minutes to properly feed it, yet it wouldn't be able to get its own food since it could hardly stay in one place. I let it go, and it stayed put for a few moments before drifting to the bottom, rising a little, and falling again. I guess that the only thing I can do now is wait, but I'm still scared for my poor little fishes.

EDIT: A few minutes ago, I walked downstairs to find my poor little Thriller dead.


Okay, now for my second question -- I'll try to make this one more brief. I have a 75-gallon aquarium with a wet/dry biolfilter and about fifteen to twenty pounds of live rock (I plan to get a bit more once it's cycled!). I would pretty much be happy with most fish at this point, yet I really have become enthralled with the snowflake eel and volitan lionfish. Don't get me wrong, and eel or lionfish would be great, yet I just can't take my eyes away from these particular breeds. I don't think I'll have any problem with the snowflake eel, yet when I read up on the volitan, most sources said that they needed a minimum of anywhere from thirty to 120 gallons of water!
I'm sure that the lionfish wouldn't be happy in a thirty gallon tank, yet I'm beginning to worry that my 75-gallon aquarium would not be enough for this fish. I've been told not to worry by a few people at my local fish store, yet I'd really like a second (or third... or fourth...) opinion from you guys. I know that most people in this guild know most about freshwater fish, yet I'm desperate by now to find out if my "dream fish" would work out in my tank.
Thanks a bunch,
Ego

 

[BluDragon35]

Wow, that took a while to read. Okay, so to answer your first question, yes, your damsels are that aggressive. And all fish will eat their dead comrades even if they are well fed. Your damsel and clown should be alright together. Just make sure that if you get new fish that the new fish are the same size as Annie and Billie Jean. You wouldn't want to get too many fish for that tank though, 30 gallons aren't really suited to be a saltwater tank. They can handle a few salt water fish but not too many. So you're good for now.

On to your next question, you should get rocks now, even if your tank isn't cycled. What happens is that the cycling builds up your bacteria colony, so you want a pretty good size colony for your saltwater tank. The bacteria lives in the sand and the filter, but mostly they are in the rocks. That's why they are called "live rock". So the more rocks you have to begin with the faster your tank will establish itself, if you add slowly the water will always be cycling until you finish adding rocks, by having a lot of rocks to begin with the bacteria won't need to expand as much when you decide to add more later on. But yah, in my own oppinion, it is better to have more rocks to begin with than to just start off slowly.

Ok, for your volitans lion....the reason they suggest such a large tank is because they are the largest species of lion. They can grow up to 18 inches I believe. Mebbie even more. If you want 3 or 4 of these crazy guys you're gonna need at least a 300 gallon tank....even that might be a bit small for 4 of thos guys. You're 75 gallon is just big enough for one lion, just. And I don't believe you would want any other fish in there other than the lion and the eel. Mebbie a puffer fish would go with that....but yah. You run a risk with aggressive fish. xp  

[Egotistical Moose]

Thanks a bunch for replying! ^^

But the thing is that the fish wasn't dead. After further inspection, I've noticed a small black dot on the damsel that killed the smallest one -- it's a whole different species of fish. Though it hasn't bothered Billie Jean or the remaining damsel and they all seem to be getting along fine, I'm considering taking it back, since its species is a much more aggressive one (though more attractive, in my opinion!) I'm definitely not considering getting any more fish for the smaller tank.

I think that I mentioned in my first post that I actually have around fifteen to twenty pounds of live rock in my 75-gallon tank to help cycle the tank. I plan on getting a bit more (not too much!) after it's been cycled.

I definitely agree with you. If one lionfish and eel could be a hassle, I'm not going to risk getting more than one of each. I think that Lionfish are aggressive to puffers, as well, so I'm considering perhaps getting a dwarf angelfish and nothing else except for some armored crustaceans and perhaps a maxima clam or two (I can't help it! They're too pretty!).

Thanks again for your help! 3nodding